Coupling



FIG. 1 is a perspective view of a coupling;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines shown in the drawings illustrate portions of the coupling that form no part of the claim. 

CLAIM The ornamental design for a coupling, as shown and described. 